This invention relates to scavenging devices within a development apparatus of electrostatographic copiers and printers for recovering unwanted charged carrier particles (DPU) from the image-bearing surface of each such copier or printer. More particularly, the invention relates to such a scavenging device that is electrostatically biased, and which is simple, effective and relatively less expensive to operate.
The use of development material consisting of charged carrier particles and charged toner particles for toner particle development of latent electrostatic images in electrostatographic copiers and printers is well known. During such development, the charged toner particles, but not the charged carrier particles, are expected to be attracted to the electrostatic latent images thereby developing them. One well known problem associated with such image development involves some carrier particles (DPU) that unwontedly are attracted along with the toner particles to the image-bearing surface of the copier or printer.
The use of various types of scavenging devices for recovering such unwanted carrier particles (DPU) from the image-bearing surface is also well known. For example, rotatable magnetic scavenging devices are disclosed in U.S. Pat. No. 3,457,900, issued July 29, 1969 to R. A. Drexler, and U.S. Pat. No. 4,466,728, issued Aug. 21, 1984 to Schlageter et al. Typically, such conventional scavenging devices require and include several other components, particularly a separate means for driving the roller therein in order to operate effectively. As such, they are relatively expensive, and in addition, their effectiveness can be affected by the failure of any such required additional components.